Field of the Invention
The present invention is related to with biocompatible polysaccharide-based hydrogels, components thereof and their use as delivery vehicles for proteins, oligonucleotides, pharmaceutical agents and cells.
Background of the Invention
Polymeric hydrogels have found a broad range of pharmaceutical and biomedical applications due to their three-dimensional structural and their functional similarity to natural tissues. A wide variety of hydrogels have been prepared, based on either physical or chemical crosslinking methods. The chemical crosslinking approach to designing biodegradable hydrogels is desirable because they are relatively easy to formulate by controlling experimental parameters, such as the type and concentration of crosslinking agents, initiator concentrations, and the ratios and concentrations of precursors.
Although many different types of polymeric hydrogels have been developed since the 1950s (Kopecek, J. Nature 2002, vol. 417, pp. 388-391), they all fall into one of two basic categories of polymer: natural or synthetic. Natural polymers have gained interest over the past few decades because of their biocompatibility and the presence of biologically recognizable groups to support cellular activities (Van Tomme et al. Expert Rev. Med. Dev. 2007, vol. 4, pp. 147-164). Among the natural polymers, dextran is a colloidal, hydrophilic, biocompatible, and nontoxic polysaccharide composed of linear α-1,6-linked D-glucopyranose residues with a low fraction of α-1,2, α-1,3 and α-1,4 linked side chains. Also, dextran can be biodegraded by dextranase, which exists in mammalian (including human) tissues. From a structural point of view, dextran has reactive hydroxyl groups (i.e. —OH) that can be modified to form hydrogels via crosslinking by photochemical and other means. As dextran is naturally resistant to protein adsorption and cell adhesion, modification of its polymer backbone allows development of a hydrogel with specific characteristics. Because of these properties, dextran and its hybrids have been extensively investigated as drug and/or gene carriers. For examples, dextran-based biomaterials have been employed in cell immobilization (Massia et al., Biomaterials, 2000, vol. 21, pp. 2253) and gene transfection (Azzam et al., Macromol. Symp., 2003, vol. 195, p. 247) and as carriers for a variety of pharmaceutically active drugs (de Jong et al., Macromolecules, 2000, vol. 33, p. 3680; Kim et al., J. Biomater. Appl., 2000, vol. 15, p. 23; Won et al., Carbohydr. Polym., 1998, vol. 36, p. 327; Kim et al., Arch. Pharma. Res., 2001, vol. 24, p. 69; Chu, C. C., in: Biomaterials Handbook—Advanced Applications of Basic Sciences, and Bioengineering, D. L. Wise (Ed.), p. 871. Marcel Dekker, New York, N.Y. (2003); Won et al., in: Biomaterials & Engineering Handbook, D. L. Wise (Ed.), p. 356. Marcel Dekker, New York, N.Y. (2000); Zhang et al., J. Biomater. Appl., 2002, vol. 16, p. 305; Peppas et al., Europ. J. Pharma. Biopharma., 2000, vol. 50, p. 27; Van Tomme et al., Biomaterials, 2006, vol. 27, p. 4141).
Many attempts have been made to engineer dextran-based polymers for various applications (Heinze et al., In Polysaccharides Ii, Springer-Verlag Berlin: Berlin, 2006; p. 199). Van Tomme et al. recently reviewed both chemically and physically crosslinked dextran-based hydrogels that were developed for protein release (Van Tomme et al. Expert Rev. Med. Dev. 2007, vol. 4, pp. 147-164). To generate chemically crosslinked dextran hydrogels, the major modification challenge is to introduce polymerizable bonds for efficient crosslinking. A common approach is to incorporate vinyl groups via different types of acrylates, thus enabling photocrosslinking. Such acrylates include glycidyl acrylate (Edman, et al., I. J. Pharm. Sci. 1980, vol. 69, pp. 838-842), glycidyl methacrylate (Vandijkwolthuis et al., Macromolecules, 1995, vol. 28, pp. 6317-6322), methacrylate (Kim et al., J. Biomed. Mater. Res., 2000, vol. 53, pp. 258-266; Ferreira et al., Biomaterials, 2007, vol. 28, pp. 2706-2717), acrylate (Zhang et al., J. Polym. Sci. Polym. Chem., 1999, vol. 37, pp. 4554-4569) and hydroxyethyl methacrylate (vanDijkWolthuis et al., Macromolecules, 1997, vol. 30, pp. 4639-4645; vanDijkWolthuis et al., Polymer, 1997, vol. 38, pp. 6235-6242). These hydrogels were proven to be efficient protein carriers. Chu et al. also developed maleic-anhydride- and allyl-isocyanate-(AI—) based dextran hydrogels (Kim et al., J. Biomed. Mater. Res., 2000, vol. 53, pp. 258-266; Zhang et al., J. Polym. Sci. Polym. Chem., 2000, vol. 38, pp. 2392-2404), which were shown to have tunable properties. Other than UV photocrosslinking, the Schiff reaction has also been employed to form crosslinks by oxidizing dextran rings into aldehyde groups (Maia et al., “Synthesis and characterization of new injectable and degradable dextran-based hydrogels,” Polymer, 2005, vol. 46, pp. 9604-9614; Ito et al., Biomaterials, 2007, vol. 28, pp. 3418-3426).
One approach to preparing dextran-based hydrogels involves the use of a synthetic polymer precursor so that the resulting hydrogels can have both synthetic and naturally occurring polymers within a single entity. Among synthetic polymer precursors that coupled with dextran, polyethylene glycol) (PEG) is popular because it is a unique amphiphilic, biocompatible but non-biodegradable polymer, and has been explored for many biomedical applications. Though PEG is not biodegradable, lower molecular weight PEG can be readily excreted from the body via kidney and liver, thereby making it more suitable for drug delivery. In addition, PEG has also been employed to improve biocompatibility (Zhang et al., Biomaterials, 2002, vol. 23, p. 2641-2648; Chung et al., Int. J. Biol. Macromol., 2003, vol. 32, p. 17), promote peptide immobilization (Hem et al., J. Biomed. Mater. Res., 1998, vol. 39. p. 266; Wang et al., J. Membr. Sci., 2002, vol. 195, p. 103), prolong protein drug circulating time (Koumenis et al., Int. J. Pharma., 2000, vol. 198, p. 83; Greenwald et al., Adv. Drug Deli. Rev., 2003, vol. 55, p. 217), increase bioactivity (Muslim et al., Carbohydr. Polym., 2001, vol. 46. p. 323-330) and reduce immunogenicity (Hu et al., Int. J. Biochem. Cell. Biol., 2002, vol. 34, p. 396-402).